xref: /llvm-project/clang/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp (revision 49b1e38e4bee0f0c6f8b49e1a62d5284084e09e7)
1 //=== StackAddrEscapeChecker.cpp ----------------------------------*- C++ -*--//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines stack address leak checker, which checks if an invalid
11 // stack address is stored into a global or heap location. See CERT DCL30-C.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "ClangSACheckers.h"
16 #include "clang/StaticAnalyzer/Core/Checker.h"
17 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
19 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
20 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
21 #include "clang/Basic/SourceManager.h"
22 #include "llvm/ADT/SmallString.h"
23 using namespace clang;
24 using namespace ento;
25 
26 namespace {
27 class StackAddrEscapeChecker : public Checker< check::PreStmt<ReturnStmt>,
28                                                check::EndPath > {
29   mutable llvm::OwningPtr<BuiltinBug> BT_stackleak;
30   mutable llvm::OwningPtr<BuiltinBug> BT_returnstack;
31 
32 public:
33   void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const;
34   void checkEndPath(CheckerContext &Ctx) const;
35 private:
36   void EmitStackError(CheckerContext &C, const MemRegion *R,
37                       const Expr *RetE) const;
38   static SourceRange GenName(raw_ostream &os, const MemRegion *R,
39                              SourceManager &SM);
40 };
41 }
42 
43 SourceRange StackAddrEscapeChecker::GenName(raw_ostream &os,
44                                           const MemRegion *R,
45                                           SourceManager &SM) {
46     // Get the base region, stripping away fields and elements.
47   R = R->getBaseRegion();
48   SourceRange range;
49   os << "Address of ";
50 
51   // Check if the region is a compound literal.
52   if (const CompoundLiteralRegion* CR = dyn_cast<CompoundLiteralRegion>(R)) {
53     const CompoundLiteralExpr *CL = CR->getLiteralExpr();
54     os << "stack memory associated with a compound literal "
55           "declared on line "
56         << SM.getExpansionLineNumber(CL->getLocStart())
57         << " returned to caller";
58     range = CL->getSourceRange();
59   }
60   else if (const AllocaRegion* AR = dyn_cast<AllocaRegion>(R)) {
61     const Expr *ARE = AR->getExpr();
62     SourceLocation L = ARE->getLocStart();
63     range = ARE->getSourceRange();
64     os << "stack memory allocated by call to alloca() on line "
65        << SM.getExpansionLineNumber(L);
66   }
67   else if (const BlockDataRegion *BR = dyn_cast<BlockDataRegion>(R)) {
68     const BlockDecl *BD = BR->getCodeRegion()->getDecl();
69     SourceLocation L = BD->getLocStart();
70     range = BD->getSourceRange();
71     os << "stack-allocated block declared on line "
72        << SM.getExpansionLineNumber(L);
73   }
74   else if (const VarRegion *VR = dyn_cast<VarRegion>(R)) {
75     os << "stack memory associated with local variable '"
76        << VR->getString() << '\'';
77     range = VR->getDecl()->getSourceRange();
78   }
79   else if (const CXXTempObjectRegion *TOR = dyn_cast<CXXTempObjectRegion>(R)) {
80     os << "stack memory associated with temporary object of type '"
81        << TOR->getValueType().getAsString() << '\'';
82     range = TOR->getExpr()->getSourceRange();
83   }
84   else {
85     llvm_unreachable("Invalid region in ReturnStackAddressChecker.");
86   }
87 
88   return range;
89 }
90 
91 void StackAddrEscapeChecker::EmitStackError(CheckerContext &C, const MemRegion *R,
92                                           const Expr *RetE) const {
93   ExplodedNode *N = C.generateSink();
94 
95   if (!N)
96     return;
97 
98   if (!BT_returnstack)
99    BT_returnstack.reset(
100                  new BuiltinBug("Return of address to stack-allocated memory"));
101 
102   // Generate a report for this bug.
103   llvm::SmallString<512> buf;
104   llvm::raw_svector_ostream os(buf);
105   SourceRange range = GenName(os, R, C.getSourceManager());
106   os << " returned to caller";
107   BugReport *report = new BugReport(*BT_returnstack, os.str(), N);
108   report->addRange(RetE->getSourceRange());
109   if (range.isValid())
110     report->addRange(range);
111 
112   C.EmitReport(report);
113 }
114 
115 void StackAddrEscapeChecker::checkPreStmt(const ReturnStmt *RS,
116                                         CheckerContext &C) const {
117 
118   const Expr *RetE = RS->getRetValue();
119   if (!RetE)
120     return;
121 
122   SVal V = C.getState()->getSVal(RetE, C.getLocationContext());
123   const MemRegion *R = V.getAsRegion();
124 
125   if (!R || !R->hasStackStorage())
126     return;
127 
128   if (R->hasStackStorage()) {
129     // Automatic reference counting automatically copies blocks.
130     if (C.getASTContext().getLangOptions().ObjCAutoRefCount &&
131         isa<BlockDataRegion>(R))
132       return;
133 
134     EmitStackError(C, R, RetE);
135     return;
136   }
137 }
138 
139 void StackAddrEscapeChecker::checkEndPath(CheckerContext &Ctx) const {
140   ProgramStateRef state = Ctx.getState();
141 
142   // Iterate over all bindings to global variables and see if it contains
143   // a memory region in the stack space.
144   class CallBack : public StoreManager::BindingsHandler {
145   private:
146     CheckerContext &Ctx;
147     const StackFrameContext *CurSFC;
148   public:
149     SmallVector<std::pair<const MemRegion*, const MemRegion*>, 10> V;
150 
151     CallBack(CheckerContext &CC) :
152       Ctx(CC),
153       CurSFC(CC.getLocationContext()->getCurrentStackFrame())
154     {}
155 
156     bool HandleBinding(StoreManager &SMgr, Store store,
157                        const MemRegion *region, SVal val) {
158 
159       if (!isa<GlobalsSpaceRegion>(region->getMemorySpace()))
160         return true;
161 
162       const MemRegion *vR = val.getAsRegion();
163       if (!vR)
164         return true;
165 
166       // Under automated retain release, it is okay to assign a block
167       // directly to a global variable.
168       if (Ctx.getASTContext().getLangOptions().ObjCAutoRefCount &&
169           isa<BlockDataRegion>(vR))
170         return true;
171 
172       if (const StackSpaceRegion *SSR =
173           dyn_cast<StackSpaceRegion>(vR->getMemorySpace())) {
174         // If the global variable holds a location in the current stack frame,
175         // record the binding to emit a warning.
176         if (SSR->getStackFrame() == CurSFC)
177           V.push_back(std::make_pair(region, vR));
178       }
179 
180       return true;
181     }
182   };
183 
184   CallBack cb(Ctx);
185   state->getStateManager().getStoreManager().iterBindings(state->getStore(),cb);
186 
187   if (cb.V.empty())
188     return;
189 
190   // Generate an error node.
191   ExplodedNode *N = Ctx.addTransition(state);
192   if (!N)
193     return;
194 
195   if (!BT_stackleak)
196     BT_stackleak.reset(
197       new BuiltinBug("Stack address stored into global variable",
198                      "Stack address was saved into a global variable. "
199                      "This is dangerous because the address will become "
200                      "invalid after returning from the function"));
201 
202   for (unsigned i = 0, e = cb.V.size(); i != e; ++i) {
203     // Generate a report for this bug.
204     llvm::SmallString<512> buf;
205     llvm::raw_svector_ostream os(buf);
206     SourceRange range = GenName(os, cb.V[i].second,
207                                 Ctx.getSourceManager());
208     os << " is still referred to by the global variable '";
209     const VarRegion *VR = cast<VarRegion>(cb.V[i].first->getBaseRegion());
210     os << *VR->getDecl()
211        << "' upon returning to the caller.  This will be a dangling reference";
212     BugReport *report = new BugReport(*BT_stackleak, os.str(), N);
213     if (range.isValid())
214       report->addRange(range);
215 
216     Ctx.EmitReport(report);
217   }
218 }
219 
220 void ento::registerStackAddrEscapeChecker(CheckerManager &mgr) {
221   mgr.registerChecker<StackAddrEscapeChecker>();
222 }
223